A variety of climbing aids are known in the art and they include spring loaded camming devices. Spring loaded camming devices are discussed in U.S. Pat. No. 4,184,657, issued to Jardine; U.S. Pat. No. 4,643,377, issued to Christianson; and U.S. Pat. No. 5,860,629 issued to Reed (the inventor herein). These devices are typically classified as symmetric or asymmetric. In a symmetric device, the head of the cam is substantially centered about the stem to which a climbing rope is attached, while in an asymmetric device, the head of the cam is not centered about the stem, but rather offset therefrom. These aids may be inserted in “cracks” and crevices during a climb and the provision of symmetric and asymmetric devices provides a climber with a wider selection of climbing aids depending on the geometry of the rock feature and the expected position of the rope. U.S. Pat. No. 4,184,657 discloses a symmetric camming device and U.S. Pat. No. 5,860,629 discloses an asymmetric camming device.
Conventional symmetric and asymmetric camming devices may include cams that are pivotally connected to the head and are biased for outward movement. From each cam, a trigger wire extends to a swaged coupling where it is fastened to a trigger cable. The trigger cable in turn connects to a trigger handle that is mounted for movement along the stem. In use, a climber pulls the trigger handle down the stem which in turn pulls through the trigger cables, swaged couplings, and trigger wires to retract the cams. The device is then positioned in a crack or crevice and the user releases the trigger handle permitting the cams to extend outward and engage the rock. This action may be repeated a few times in an attempt to achieve secure placement in the crack.
In a conventional spring loaded camming device, there are typically four cams arranged in two cam pairs. Each cam pair has a five part trigger linkage that includes two trigger wires, two swaged couplings and a common trigger cable. Thus, in a conventional camming device, the trigger mechanism includes 10 pieces and a trigger plate or handle.
While trigger systems of this type have been used for many years, they have disadvantageous aspects that include the following. Firstly, the trigger system is expensive. It has many parts and they are carefully assembled by hand, which is one of the most difficult and time consuming tasks associated with manufacturing. Secondly, each part may have a given variance in size, shape or other quality and the cumulative variations are problematic to the manufacturing process and the quality of the finished product. Thirdly, the devices are fairly fragile and the trigger cables are long and unprotected. The cable easily tangled with other gear. In addition, the cables wear out due to being repeatedly flexed and twisted. Fourthly, where the trigger cables pass through the trigger must be centered precisely during manufacturing to balance the initial orientation of the cam head relative to the trigger. The cables are typically glued there to prevent them from moving. This is both cost and time consuming, and misalignment results in a defective product.
A need exists for a camming device with a trigger mechanism that has fewer components and one with a simpler, more durable design.
Another problem associated with spring loaded camming devices relates to their stability in a crack, or the lack thereof. For a camming device to be reliable, it must be stable and retain its holding power, even if the camming device moves slightly in the crack after it is initially placed.
There are two main causes of cam movement. The first is associated with forces exerted by a climbing rope on the stem as the rope moves from side to side or front to back (normal motion during climbing). Movement of the stem can be transferred to the cams causing them to reposition themselves or “walk” in a crack. A need exists to provide a camming device in which the transfer of force from the stem to the cams is reduced.
Another cause of cam movement that is more often experienced in asymmetric camming devices is an occurrence referred to as “tipping out.” It is a common practice among climbers to adjust the position of the cams by pushing from the stem. In a symmetric camming device, the “pushing force” is more equally distributed since the head is aligned with the stem. In an asymmetric camming device, however, the head is not centered and one cam may move more than the other causing de facto rotation of the device about the distal end of the lesser moving or inner cam. If the inner cam rotates too far, it may move past its' “toothed” surface and may slip, resulting in a failure of the device to hold in the crack. Tipping out in an asymmetric camming device may also occur from “normal” rope motion. A need exists to improve an asymmetric camming device such that the incidence of tipping out is greatly reduced or eliminated.